FIELD OF THE INVENTION
The invention relates to a steam generating power plant having a steam turbine driving a generator and a steam bleeder line connected to the steam turbine. The invention also relates to a process for operating a steam generating power plant and to an interlinking network to which a number of steam generating power plants are connected. The invention additionally relates to a process for operating the interlinking network.
Steam generating power plants of the type referred to above are conventional and well known in the art.
In relatively large power supply systems, the objective arises of accumulating certain quantities of energy for the sake of keeping available what is known as "seconds-order reserve power". That objective arises from the necessity of keeping virtually spontaneously activatable electric power constantly available in that system in the event that sudden unpredictable power deficits occur, for instance from power plant failure.
In the UCPTE network (European Interlinking Network), every plant must keep available 2.5% of the instantaneous network load as "seconds-order reserve power". In the Federal Republic of Germany, half of the "seconds-order reserve power" must be activatable within five seconds, and the remainder within a further 25 seconds, to enable compensating for a power deficit in the public network. At present, preserving the "seconds-order reserve power" is done by throttling the turbine adjusting valves in the steam generating power plants that feed into the interlocking network, but that involves losses. In other words, such steam generating power plants are operated in throttled fashion. Upon a network load peak, or in other words a deficit of the total power plant output being supplied, that throttling is reduced, thus increasing the output of the steam generating power plants accordingly. It is a peculiarity of the throttling that because of the somewhat reduced efficiency, operating costs for the individual power plant correspondingly rise. Moreover, that type of power deficit compensation requires that the various steam generating power plants be built for somewhat greater capacity than would otherwise be the case. That accordingly increases investment costs as well. It would be desirable if the throttling could be avoided, so that both operating and investment costs could be kept low.
In order to compensate for power deficits within the range of from 30 seconds to 5 minutes or more in duration, it is already known to briefly suppress steam supply to feedwater preheaters, which are heated with bled steam, or in other words to undertake a shutoff of preheaters (as is the publication VGB Kraftwerkstechnik [VGB Power Plant Technology] 60, No. 1, January 1980, pp. 18-23). That provision makes an increased quantity of steam available immediately to the steam turbine. The time thus gained is usually sufficient to run the heating output in the steam generator up to the allowable limit output, if lesser load peaks are expected, or to activate pump accumulator power plants or gas turbine power plants. Leveling load peaks by briefly closing the valve in the steam bleeder line does not increase operating costs. However, it is a peculiarity of that type of leveling of load peaks that it responds with a delay which is on the order of 20 to 40 seconds, depending on the type of power plant. It is therefore unsuitable for leveling load peaks fast enough that there is no interruption in output or a drop in frequency. The term load peaks is understood in this case to mean especially sudden, unpredictable power deficits on the part of the power generator, of the kind that arise, for instance, from power plant failures. Load peaks that arise from a sudden connection of large-scale consumers, in large interlocking networks such as the European Interlocking Network, in contrast to isolated networks with only a few power plants, have only secondary significance.
In electrical energy supply, the provision of Superconducting Magnetic Energy Accumulators is also known (from the publication BWK, Vol. 40, 1988, No. 9, pg. 353-360, particularly FIG. 10, and the publication "Elektrizitatswirtschaft" [Electrical Industry], Vol. 89, 1990, No. 3, pp. 111-115). Power fluctuations in the electrical network can thus be compensated for. Therefore the peak demand in a network can also be covered, even for up to several hours. However, such superconducting magnetic energy accumulators have not yet been considered for furnishing the seconds-order reserve power, where the important factor is to have high capacities available for an interlocking network within a relatively brief period of time.